My response to what you said is in the hide tags.

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I'm going to try my best to keep emotion out of this and simply explain why you're wrong. First of all, his Gengar doesn't have Taunt, so I'm not sure why it's relevant that "Taunt Gengar beats Chansey 1 on 1." Even if one were to suggest Taunt, that doesn't really make Gengar some sort of premier stallbreaker, given that it does about 30% to Chansey with Focus Blast (assuming Focus Blast actually hits) while the other moves probably do about half of that. Life Orb eats 10% of its health with each hit, meaning it can only attack 10 times before it's dead and even less if it has to take any other sort of damage. You also fail to consider that his opponent can do this thing called switching out, which means he doesn't have actually have to 1v1 Gengar with Chansey.

"Ferro and Mag and stuff are well covered" is a pretty lousy reason to use an SD Talonflame that can't beat Metagross, Excadrill, Thundurus, Raikou, Zapdos, (pre-mega) Manectric, and possibly even a bulky SD Scizor along with, of course, Ferrothorn and Magnezone. You even named Excadrill as a threat yourself (and included Flare Blitz in your importable), but you still want to say Flare Blitz isn't needed? I don't see any argument here.

Raikou gives him something to revenge opposing SD Talonflame as well as outspeed and threaten Weavile and certain scarfers that annoy him, like Landorus-T and Garchomp. Though Scarf Raikou isn't the greatest mon, it's still doing more than Assault Vest Raikou, since it checks electric types even without Assault Vest and has equal strength.

I could go on to pick apart the flaws in your rate, but I'm not going to do that because it's not my role. We give advice, and the OP decides whether or not to take it. We don't badmouth the advice of others and argue over whose advice is best.